This is R3 model released, with integrated micro-SD card reader, additional pins (I2C and IOREF) and compatible with Arduino Mega.

Ethernet Shield is extension module put on top of Arduino and using its power supply, providing Ethernet connectivity.

With Ethernet library from Arduino IDE, You can easily connect Arduino to IP network (Internet!) to send and receive data. Using this library you are able to easily write sketches receiving and transmittiong data in Ethernet network.

This module is based on Wiznet W5100 chip with implemented TCP/IP stack, so Ethernet library from Arduino IDE doesn't take much space on Arduino's Flash memory.

Apart from the previous Ethernet Shield version, this one has SD card reader onboard, along with reset button. What's more, it's PoE ready. This means you can power Arduino with the shield mounted through Ethernet cable (CAT5 cable compliant with the 802.3af standard). In order to do so, you will need also additional PoE module sold separately.

NOTE:This shield works with Arduino Mega without the need of any modifications, in opposition to the older version. This regards Arduino Mega 2560 as well as the older one, based on ATmega 1280.